Re: Why single coil at neck?
The first one I saw use that config was Lynch, and he used the neck for cleans and the bridge for distortion. Since he turned out to be an influential player, I'm assuming that's what most people were going for when they went with H-S, or even H-S-S to get those position 4 neck+middle Strat tones. Middle+Bridge became irrelevant, but since you can't get neck+middle single coil tones easily without H-S-S and a 5-way, that's how it was.
Then you also have those who can't pick properly complaining about the middle single getting in the way, and again, they only use the neck for cleans, and want Strattish neck single clean tones. This is also why you typically see the neck pickup being the only one set up for splitting, so they can get both Strattish neck cleans and humbucker distorted lead tones ala Dave Murray.